Shade is often regarded as a disadvantage in gardens because it limits the choice of flowering shrubs and perennials that can be grown.
Many evergreen and deciduous foliage shrubs thrive, and some herbaceous subjects such as hellebores, pulmonarias and digitalis bloom happily, but flowering shrubs are relatively few, especially during summer and autumn. Hydrangeas are the exception. Most are happier in light shade than they are in sunny positions and they bloom for months rather than weeks.
As the name suggests, hydrangeas like water. They are very happy on clay and moist soils, however some seem to adapt to much drier conditions, especially if they are not exposed to hot sunshine.This makes them ideal to grow under the light shade of deciduous trees where the soil is probably enriched by plenty of organic matter from leaf fall.
The cultivars of Hydrangea paniculata are some of the most useful, flowering from mid-summer through to autumn depending on variety. The conical flower heads vary from bold panicles of large sterile florets to lacy mixtures of starry sterile ones and tiny beaded fertile flowers. Both can remain attractive as they turn to parchment through winter.Pruning in late winter promotes strong, upright shoots; cut back to a strong framework each year.
Hydrangea paniculata is particularly useful amongst dark evergreens such as Aucuba japonica ‘Rozannie’ and Viburnum davidii. Underplant with variegated Euonymus fortunei ‘Emerald Gaiety’. Perfect to brighten up a shady bed or border.
Hydrangea arborescens ‘Annabelle’ is one of the best known hydrangeas. The large, sponge-like white flowerheads and soft green leaves are unmissable in the second half of summer. It looks wonderful under white barked birches with silvery miscanthus and dark sarcococcas. Plant where it can borrow support from other plants as the stems can bend and flop under the weight of the flowerheads. Opinions vary on how hard to prune, but there is no doubt that it needs cutting back in late winter to a few centimetres from ground level. Great to fill a shady corner and excellent on chalk.
The oak-leaved hydrangea, Hydrangea quercifolia is just as valued for its architectural foliage as it is for its flowers. Its habit can be rather ungainly, so it is never one of the most popular. Where it gets a reasonable amount of sunshine the foliage takes on rich tints in autumn. In shade the leaves are deep green. Flower heads are similar to those of Hydrangea paniculata, but often more pendant. Hydrangea quercifolia ‘Snowflake’ is one of the most spectacular with massive sprays of double, creamy-white florets.
Hydrangea serrata has finer stems and smaller leaves than the familiar Hydrangea macrophylla.Whereas the latter has big leaves and flowers, Hydrangea serrata has small lacecap flower heads which are light and delicate in character and seem to be more drought resistant than the larger growing varieties.Hydrangea serrata ‘Bluebird is a well-known, free-flowering cultivar. The delicate blooms are mauve-pink on alkaline soil but gentian blue in acid conditions. Even in shade the foliage is flushed with plum purple from late summer onwards.
Many of the pink and red-flowered cultivars of Hydrangea macrophylla will also “blue” on acid soil. For those with soil of a higher pH blue flowers can be achieved by growing in a pot of ericaceous compost and watering with hydrangea colourant on a regular basis. The purple-pink blooms are every bit as attractive, but for some reason blue hydrangeas are always especially desirable.
Hydrangea macrophylla varieties have two different flower forms. Some are known as mopheads, these are the ones with big, bold heads of large, sterile florets. The others are the lace-cap hydrangeas. These have heads of small fertile florets surrounded by a ring of larger sterile ones.The lacecaps are more attractive to pollinators. Hydrangea macrophylla ‘Zorro’ is a lovely lacecap hydrangea with black stems and blooms that turn vivid blue on acid soil, even in shade.
White flowered Hydrangea macrophylla varieties never change colour according to soil type.However in sun, or when affected by weather they may become flushed with pink or even deep blue. Hydrangea macrophylla ‘Madame Emile Moulliere is one of the best white mophead hydrangeas which will take on pinkish hues around the edges of the florets when grown in sun, however, in shade the flowers remain pure white.
Secrets of success
Although some of these hydrangea varieties are more drought tolerant when established, newly planted plants need regular watering to ensure success.
Although remarkably hardy, hydrangeas can be caught with frost as new growth emerges in spring. Where possible avoid planting them where this could be an issue. Hydrangea paniculata tends to be more resistant to spring frosts.
Feed hydrangeas annually with a slow release fertiliser recommended for flowering shrubs. Fertilisers that are high in potash help to harden the growth and stimulate flower production.
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